What is septicemia?

Causes and Symptoms

The rapid multiplication of bacteria and the presence of their toxins in the blood is a condition commonly known as blood poisoning, septicemia, or bacteremia. It is always an extremely serious condition and represents a medical emergency that requires the prompt medical intervention. A person in whom septicemia develops suddenly becomes seriously ill with a high fever, chills, rapid breathing, headache, and often clouding of consciousness. Skin
rashes or
jaundice may occur, and sometimes the hands are unusually warm. In many cases, especially when large amounts of toxins are produced by the circulating bacteria, the person passes into a state of septic shock, which is life-threatening.

Bacteria in the bloodstream can produce two different types of complications: microbiologic and inflammatory. The microbiologic complications result from the local and systemic proliferation and seeding of the bacterial causative organism, which causes direct tissue or organ damage. The inflammatory complications are produced locally and can result in tissue or organ destruction independent of the toxic factors produced by the causative organism. Bacteremia triggers intravascular activation of the same inflammatory systems that are protective within tissues. These systems, which combine with stress-generated endocrine responses, produce a sequence of metabolic events, the end stage of which is the systemic vascular collapse traditionally called septic shock.

Shock symptoms vary with the extent and site of major tissue damage. They are similar to those for septicemia, with additional symptoms including cold hands and feet, often with blue-purple coloration caused by poor blood flow; a weak, rapid pulse; and markedly reduced blood pressure. There may be vomiting and diarrhea, and a poor output of urine may indicate that damage to the kidneys is occurring and that there is risk of renal failure. Heart failure and abnormal bleeding may also occur.

Septic shock is a dangerous condition in which there is tissue damage and a dramatic drop in blood pressure as a result of septicemia. Septic shock is usually preceded by signs of severe infection, often of the genitourinary or gastrointestinal systems. Fever, tachycardia, increased respiration, and confusion or coma may occur during shock. The classic septic shock
syndrome results primarily from the sequence of events triggered by bacteremia, during which the bacterial toxins activate compounds that impair the functioning of surrounding cells in several ways. In many cases, the bacterial toxins are the main cause of trouble because they can cause damage to cells and tissues throughout the body and promote clotting of blood in the smallest blood vessels, seriously interfering with circulation. Consequently, damage occurs especially to tissues in the kidneys, heart, and lungs. The bacterial toxins may cause leakage of fluid from blood vessels and a reduction of the ability of the vessels to constrict, leading to a severe drop in blood pressure. Therefore, septic shock is a systematic vascular collapse, in which the systolic blood pressure of the patient is less than 90 millimeters of mercury. In septic shock, the low blood pressure has become unresponsive to adequate volume replacement. Morbidity and mortality associated with septic shock are high: About two-thirds of patients die.

Septicemia and septic shock can precipitate multiple organ failure. As the patient becomes hypermetabolic and febrile with progressive failure of one or more organs, the mortality rate can be as high as 90 percent. Septicemia is most common in people hospitalized with major disorders such as diabetes mellitus, cancer, or cirrhosis and who have a focus of infection somewhere in the body (often the intestines or urinary tract). Progression to septic shock is especially likely for people who have immunodeficiency disorders or are taking immunosuppressant drugs for cancer or an inappropriate antibiotic treatment. Newborn infants are also particularly at risk if septicemia develops.

Treatment and Therapy

A presumptive diagnosis of septicemia is often made on the basis of historical, physical, and laboratory data even in the absence of proof. The setting in which the episode is occurring should be evaluated promptly. Crucial to appropriate initial decision-making are the background history, which may help to define the type of host-defense defect present, and prior blood culture data, which might predict the infecting organism. The physical examination should be quick and thorough, searching for the septic source as well as signs that might indicate progression to shock.

A diagnosis can be confirmed and the infective bacteria identified by growing a culture of the organisms from a blood sample. Several laboratory tests are often helpful in the evaluation of a potentially septic patient. In general, patients with fever should be considered septic until proved otherwise, and therapy should always be initiated for high-risk febrile patients in advance of a microbiologic confirmation of septicemia.

Common microorganisms that enter the bloodstream when the body’s defenses break down include staphylococci from boils, abscesses, and wounds; streptococci from the tonsils, throat, or cuts; and pneumococci from the lungs. Other invaders of the bloodstream include the gonococci, the typhoid bacilli in typhoid fever, and Escherichia coli (E. coli) in bowel infections. All these bacteria may be detected by taking a blood culture.

Antibacterial therapy should be started as soon as septicemia is suspected. It is normally started by intravenous infusion of antibiotic drugs and glucose and/or saline solution. The focal site of infection is sought immediately and may be surgically removed. Surgical debridement (removal) and drainage of septic foci are especially important, and all severe localized infections should be widely debrided and drained. If the infection is recognized and treated promptly, there is usually a full recovery.

Broad antibacterial coverage is required in patients with severe septicemia. It is best to initiate therapy with a combination of
antibiotics when the infecting organism is unknown. When cultures define the causative microbe(s) or other data point to a specific organism, therapy can then be tailored to the most appropriate, most specific, least toxic, and least expensive single antibiotic. Penicillin is usually used to combat staphylococcic, streptococcic, pneumococcic, and gonococcic infections; chloramphenicol and ampicillin are used against typhoid and paratyphoid infections; and neomycin is used against E. coli infections. Extreme care must be taken with the administration of chloramphenicol and neomycin because of their toxic side effects.

Antibiotics limit the microbiological complications of bacteremia, but other metabolic events, whether initiated by or independent of bacterial proliferation, may still produce substantial morbidity and mortality. Therefore, therapy in addition to antibiotics is recommended to counter this metabolic sequence.

Septic shock requires immediate treatment, including the use of antibiotics and surgery, rapid fluid replacement by infusion, and the maintenance of urine flow to prevent the effects of renal failure. Other measures must also be taken to raise the blood pressure and to promote a better supply of important nutrients to tissues, such as through intravenous infusion and oxygen therapy. The use of anti-inflammatory drugs is under active investigation.

Perspective and Prospects

Most febrile patients lacking other signs of severe septicemia will usually do well. Such patients usually respond quickly to fluid administration, antibacterial therapy, and drainage of the primary focus of infection. The presence of septic shock, however, dramatically increases morbidity and mortality. Even when the inciting infection is localized, shock is associated with at least 50 percent mortality. Full-blown septic shock has greater than 70 percent mortality. A favorable outcome in a patient in severe shock depends on the skill of management in the intensive care unit. Early diagnosis and therapy of severely septic patients will greatly decrease the morbidity and mortality of these individuals. The best means of preventing bacteremia is the proper care of burns and wounds and prompt application of antiseptic tinctures or preparations to ordinary cuts and tears.

Infections most commonly occur in the hospital setting, where many infected patients become bacteremic. About 5 percent of all hospital patients either are admitted with or develop an infection during hospitalization. This means that the number of patients at risk of developing septic shock is large. The clinician must be familiar with the manifestations and differential diagnosis of the patient who appears to suffer from septic shock and must have in mind rapid, comprehensive diagnostic and therapeutic plans of action. It is important to develop the concept of a preshock phase of septic shock predicated on identifying a subgroup of infected patients more likely than others to develop shock. In such patients, fluids should be administered and broad antibiotic coverage started early. Treatment before shock develops undoubtedly prevents some of the morbidity and mortality associated with septicemia.

Bibliography

Goldman, Lee, and Dennis Ausiello, eds. Cecil Textbook of Medicine. 23d ed. Philadelphia: Saunders/Elsevier, 2007.

Litin, Scott C., ed. Mayo Clinic Family Health Book. 4th ed. New York: HarperResource, 2009.

Mosby’s Medical Dictionary. 9th ed. St. Louis, Mo.: Mosby/Elsevier, 2012.

Rodak, Bernadette, ed. Hematology: Clinical Principles and Applications. 4th ed. St. Louis, Mo.: Saunders/Elsevier, 2011.

"Sepsis." Mayo Clinic, January 26, 2013.

"Septicemia." Medline Plus, August 24, 2011.

Strand, Calvin L., and Jonas A. Shulman. Bloodstream Infections: Laboratory Detection and Clinical Considerations. Chicago: American Society of Clinical Pathologists, 1988.

Wilson, Michael, Brian Henderson, and Rod McNab. Bacterial Disease Mechanisms: An Introduction to Cellular Microbiology. New York: Cambridge University Press, 2002.

Wood, Debra. "Blood Poisoning." Health Library, October 31, 2012.

Zucker-Franklin, D., et al. Atlas of Blood Cells: Function and Pathology. 3d ed. Philadelphia: Lea & Febiger, 2003.